Release v1.2.4

Changes since v1.1.280:

• Level: add a new secret room (thus minor version bump). VERY well hidden though :)
• Level: In Tower of Impossible: make the “impossible button” more conspicuous.
• Engine: reduced runtime memory allocation by 70%.
• Engine: update Ebiten to fix crashes on some laptops where the keyboard was detected as a gamepad with way too many buttons. Do NOT enable DirectX yet - that is for when Ebiten 2.3.0 is out :)
• Engine: do not map the Alt key - this is annoying on Windows. Use Ctrl instead.